VOCALS

2008 VAMOS Ocean-Cloud-Atmos-Land Study (VOCALS)

14 October 2008 - 13 November 2008

Lead Scientist: Peter Daum

Observatory: OSC

The DOE G-1 aircraft was deployed to Arica, Chile as part of the NSF VAMOS Ocean-Cloud- Atmospheric-Land Study (VOCALS). The purpose of VOCALS is to develop an understanding of the physical and chemical processes central to the climate system of the Southeast Pacific. In this region, extensive areas of marine clouds exist (coverage about 70% in October). The ASP component of VOCALS focused on aerosols, and how their chemical and microphysical properties, and their ability to act as CCN differ between remote marine air masses and marine air masses that have been influenced to varying degrees by anthropogenic aerosols, and how these differences in aerosol properties influence the microphysical properties of the clouds that form in these different environments. The NSF C-130 aircraft and the NOAA R/V Ronald H. Brown also collected data in the region during the G-1 flights. The data collected during this field campaign allow examination of the relationship between aerosol composition, size, and CCN activity; between CCN loading and activity and cloud droplet microphysics; between cloud droplet microphysics and cloud radiative properties (first indirect effect studies); and between cloud droplet microphysics and the formation of drizzle (second indirect aerosol effect studies). Data can also be used to examine the validity of recently developed parameterizations of cloud microphysical processes and the properties designed for use in GCMs, and to develop the physical insight needed to develop more complete and sophisticated parameterizations of these quantities. The G-1 was instrumented with its standard suite for meteorology/state parameters. Additional instrumentation allowed characterization of the chemical and microphysical properties of aerosols and the microphysical properties of clouds. Trace-gas instrumentation measured aerosol precursors (SO_2 and DMS) and species that aid in estimating anthropogenic contributions to aerosols (CO and O_3 ) in the air masses being sampled. Aerosol optical properties (absorbance and scattering), size distributions and concentrations of aerosols and clouds, aerosol chemical composition and cloud forming tendencies were all measured using a suite of research grade instruments modified for aircraft operations. Flights included below-cloud legs to measure pre-cloud aerosol properties, in-cloud flights at several altitudes to examine the relationships between pre-cloud aerosol properties, cloud dynamics and cloud droplet microphysics, and their variation with altitude, and sampling through and above cloud top to define the vertical dimensions of the cloud, to document the thermodynamic structure of the atmosphere, and to sample the properties of the above-cloud aerosols.